systemmodeler | 易学教程

What are the differences between diffferent Modelica Simulation Environments?

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问题 There are different Modelica Simulation Environments, including Dymola, Wolfram SystemModeler, OpenModelica, and Jmodelica. So, I try to load a thermal fluid library(ThermoSysPro https://github.com/Dwarf-Planet-Project/ThermoSysPro), but except Dymola, the results on the other software all end with errors. If the library and the simulation environment are all based on the Modelica Specification Standard, why there is a compatibility issue? I think that maybe the library includes some features

What are the differences between diffferent Modelica Simulation Environments?

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Including a causal relation in a Modelica simulation leads to translation Error while flattening model

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问题 I want to simulate a controller for a mass-spring model which works based on energy: model model //constants parameter Real m = 1; parameter Real k = 1; parameter Real Fmax = 3; parameter Real x0 = 1; parameter Real x1 = 2; parameter Real t1 = 1; //variables Real x, v, a, xy, vm; initial equation x = x0; v = 2; equation v = der(x); a = der(v); m * a + k * x = F; algorithm vm := sign(xy - x)*sqrt(2 * (Fmax * abs(xy - x) + k * (xy^2 - x^2) / 2) / m); // step signal if time < t1 then xy := x0;

Switch between two flanges

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问题 I am currently working with multibody mechanical systems using the MultiBody library included in the standard Modelica distribution. I need to implement a switch between flanges, in order to select position or force control for a given joint. model FlangeSwitch "Switch between flanges" Modelica.Mechanics.Translational.Interfaces.Flange_a flange_a_1; Modelica.Mechanics.Translational.Interfaces.Flange_b flange_b_1; Modelica.Mechanics.Translational.Interfaces.Flange_a flange_a_2; Modelica

How to make use of the unit attribute within a model in Modelica?

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问题 Motivation Modelica does store units of measurement (e.g. SI units and Non-SI units) as an attribute with regard to a variable. Here is an example for a Non-SI-unit: type Time_months = Real( quantity = "Time", unit = "mo", displayUnit = "months" ) Since for models in economics it will be rather akward to give rates in seconds, I would like to write a rather general unit conversion function that will allow to convert units of time. So ideally a function to convert to another time base should

Generate white noise in Modelica (SystemModeler)

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问题 I am trying to add measurement noise to a simulation. This is possible to do in for example Simulink but seems to be more difficult in Modelica and SystemModeler. Any ideas on how to do this? 回答1: An alternative is to use Modelica.Blocks.Noise to avoid writing external code yourself (added in Modelica Standard Library 3.2.2 released April 3, 2016; i.e. it would not have helped when the original question was asked). One benefit of Modelica.Blocks.Noise is that the tricky questions with

Generate white noise in Modelica (SystemModeler)

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I am trying to add measurement noise to a simulation. This is possible to do in for example Simulink but seems to be more difficult in Modelica and SystemModeler. Any ideas on how to do this? An alternative is to use Modelica.Blocks.Noise to avoid writing external code yourself (added in Modelica Standard Library 3.2.2 released April 3, 2016; i.e. it would not have helped when the original question was asked). One benefit of Modelica.Blocks.Noise is that the tricky questions with sampling, multiple seeds, etc are solved. Mikael Forsgren You can add white noise in Wolfram SystemModeler via